The objective of the proposed study is to further expand and clarify our understanding of the mechanisms by which the ovarian hormones control the structure and function of the mammalian oviduct. An attempt will be made to understand the process by which estradiol and progesterone interact to optimize the essential physical and biochemical processes in maintaining sperm and ovum viability. The techniques of light and electron microscopy, cytomorphometrics, and steroid receptor analysis will be utilized to study the oviducts removed from steroid treated ovariectomized cats, and from women in all reproductive stages and from those taking oral contraceptives. Cyclic alterations in morphology, cell height, and percentage of ciliated cells in the fimbriae, ampulla, and isthmus will be correlated with cytoplasmic receptor levels and with systemic levels of estradiol and progesterone. Estradiol and progesterone will be measured by radioimmunoassay and progesterone receptor concentration will be quantified using the exchange assay technique. The stage of the menstrual cycle will be determined by endometrial dating. This study will provide important quantitative information as to the sensitivity of the human fallopian tube in the ovarian steroids. The data obtained will be of help to the clinicians in giving them a better understanding of the problems associated with fertility. Also, a more complete understanding of the factors involved in ciliogenesis and secretion may lead us to a new approach for the development of a safe and reliable contraceptive.